Apparatus for analyzing cement kiln exit gases



Nov. 23, 1965 N. c. LUDWIG ETAL 3,

APPARATUS FOR ANALYZING CEMENT KILN EXIT GASES Filed April 50, 1963 2 Sheets-Sheet l Water In INVENTORS.

NORMA/V C. LUDW/G and STEWART W. TRESOUTH/CK A! rorney Nov. 23, 1965 N. c. LUDWIG ETAL 3,

APPARATUS FOR ANALYZING CEMENT KILN EXIT GASES Filed April 30, 1963 2 Sheets-Sheet 2 u n 3 at! Elfiiq mJ 2 m9 3 @9 u QM F lllllllllllllllllllll Ill.

.v ll 1| II S?" 4 Q2 3 g mm H u u vq n 3 2 m9 3 u u u .m m2 m9 mm mm 3 x 3 mm 3 Fl||ll.| l I l I I I l l l I l l l I I I I ||L I I I I l I l I I I |ll|L INVENTORS. NORMAN 6. LUDW/G and STEWART W. T/PESOUTH/CK By Attorney United States Patent Ofi ice 3,218,842 Patented Nov. 23, 1965 3,218,842 APPARATUS FOR ANALYZING CEMENT KILN EXIT GASES Norman C. Ludwig, Chicago, Ill., and Stewart W. Tresouthick, Norwalk, Conn., assignors to United States Steel Corporation, a corporation of New Jersey Filed Apr. 30, 1963, Ser. No. 276,802 9 Claims. (CI. 73-23) This invention relates to apparatus for analyzing cement kiln gases and more particularly for determining the corrected or True CO content of such gases. The cement kiln exit gases are made up of the products resulting from burning the coal or other fuel and certain gases evolved from the cement raw mix. The gases evolved from the cement raw mix are in large part CO For example, a coal fired kiln requires 70 lbs. of pulverized Bituminous coal per 376 lbs. of cement clinker, 606 lbs. of raw mix are required to produce this cement clinker and 218 lbs. of CO are released therefrom. This is greater than the amount of CO resulting from burning the 70 lbs. of coal. The combustion conditions will be controlled so that in most cases will be included in the exit gases. Water vapor, nitrogen and CO will also be present as well as small amounts of S0 Oxygen and CO analyzers are ordinarily used as sensors to determine combustion conditions in the kiln and hence are used to control the operation of the fuel-air proportioning systems. However, these sensors are not completely satisfactory for many reasons especially as they relate to the measurement of material flow through the kiln. We have found that the CO content of the kiln exit gases is important in monitoring and controlling the flow rate of the raw materials through the kiln. From a practical operating view point we have found that problems are present in continuously determing the CO content of cement kiln exit gases. Because of the presence of other gases in variable amounts it is expedient to determine the True CO as compared to the CO content as obtained by the use of a standard CO analyzer. The True CO content can be determined if the O and CO content of the gas is also known. The significance of True CO is discussed in detail in the Portland Cement Association Bulletin MRB-Sl entitled Kiln Test Manual wherein the following equation is set forth:

It is an object of our invention to provide apparatus for continuously analyzing kiln exit gases for CO content.

Another object is to provide such apparatus which also analyzes the exit gases for O and CO content and computes the True CO content by providing means which will solve Equation 1 from signals from the individual 0 CO and CO analyzers- These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

FIGURE 1 is a schematic view of the apparatus of our invention; and

FIGURE 2 is a schematic wiring diagram showing circuits for computing the True CO content from signals from individual analyzers.

Referring more particularly to the drawings, reference numeral 2 indicates the wall of the back housing of a rotary kiln for making cement. A water cooled sampling probe 4 passes through the wall 2 into the back housing. This is a standard device and is preferably Model N0. 664981Il0Y manufactured by Bailey Meter Company of 1050 Ivanhoe Road, Cleveland, Ohio. The probe 4 includes a reverse spray nozzle 6 at its sample True CO;

end and a spray water inlet 8 at its outer end. Cooling water for the probe enters through inlet 10 and is discharged from outlet 12. Other types of probes may be used for this purpose, but a reverse spray wet type probe is preferred to a dry type probe, especially when the gases are extremely hot and dirty. A conduit 14 for the sample gas is connected to the probe 4. An inductor 16 may be provided in the conduit 14, but this is not ordinarily used when using the reverse spray nozzle of a water washed tube. The other end of the conduit 14 is connected to a washer 18. This is a conventional device such as that shown on page 8 of Bailey Meter Company Catalogue E 65-11. A motor driven centrifugal pump 20 has an inlet 22 for make-up water and an inlet 24 connected to the bottom of washer 18. The pump 20 has an outlet 26 which is connected to an orifice 28 which in turn is connected to a recovery tube 30 which leads to a distintegrator 32. A conduit 34 connects the washer 18 to a separator trap 36. This is a conventional device such as that shown on page 9 of Bailey Meter Company Catalogue E 65-11. The separator trap 36 includes a relief valve 38, a float 40, an outlet 42 for water and dirt, a main outlet 44 for the gas. The outlet 44 is connected to a T 46. A portion of the gas passes from the T 46 through a conduit 48 to an electrically heated filter 50 which in turn is connected to an oxygen and CO analyzer block 52. This is a standard piece of equipment such as Model 0015 manufactured by Bailey Meter Company and shown in Catalogue E 658. The remaining portion of the gas passes through a conduit 54 through an electrically heated filter 56 which is preferably of the same type as filter 50. One suitable filter is shown on page 21 of Bailey Meter Company Catalogue E 658. From the filter 56 the gases pass through an inline porous element gas filter 58 which may be of a type manufactured by Mine Safety Appliance Company of Pittsburgh, Pennsylvania. From the filter 58 the gases pass through a differential pressure type flow regulator 60 such as a Fischer-Porter Purge meter regulator, Model 10A3l35N thence to a C0 analyzer 62. The analyzer 62 is preferably an infrared analyzer, such as Model LIRA sold by the Mine Safety Appliance Company, specially calibrated in the range of about 20 to 32% CO This type of analyzer includes two identical infrared beams which are directed through two gold plated polished stainless steel gas cells mounted in an optical bench (details not shown). One cell contains a known comparison gas and the other the gas which is to be analyzed. We have found it necessary to purge the housing 64 with clean, dry air of constant temperature to prevent erosion of analyzer parts from small amounts of S0 in the kiln gas. Also we have found it necessary to maintain an ambient temperature at about plus or minus 2 F. for the analyzer to hold its calibration. In order to do this a thermo regulator 66 is inserted in housing 64. This may be any standard device such as Model NS-81833 sold by E. H. Sargent Company. Air is delivered to a heater filter assembly 68 through a pressure regulator 70, a trap 72 and a valve 74. The filter heater assembly is a modification of a standard device and may be similar to filter heater assemblies 50 and 56. The filter heater assembly includes a filter 76, a heater element 78 and a thermo switch 80. The heater element 78 and thermo switch 80 are connected to a volt power source L1, L2 in series with the thermo regulator 66. The incoming air passes downwardly to the heater 78, upwardly through the filter 76 and then through a conduit 82 to the housing 64.

The CO analy'zer 62 develops an electric signal pro portional to CO which is connected to a, dual pen CO oxygen recorder 84. An electrical signal from the oxygen analyzer cells 52 is also connected to the recorder 84,

this signal being proportional to the content of the gas. An electrical signal proportional to the CO content of the gas from analyzer cells 52 is connected to a dual pen True CO CO recorder 86. The recorders 84 and 86 are standard equipment such as shown in Bailey Meter Catalogues E 12-3. While various circuits may be provided for computing True C0 that shown in FIGURE 2 is preferably used. Mounted in the recorder 86 is a movable core transformer 88 which is adjusted to give an output voltage proportional to 1.89 times the recorder CO reading-and a movable core transformer 90 adjusted to give an output voltage proportional to 100 times the recorder CO reading. Mounted in the recorder 84 is a movable core transformer 92 adjusted to give an output voltage proportional to 100 times the recorder CO reading and a movable core transformer 94 adjusted to give an output voltage proportional to 4.78 times the recorder 0 reading. A fixed voltage transformer 96 is provided to supply a constant voltage of 100 relative to other voltages. The primaries of the transformers are connected to AC. voltage source L3-L4. Precision type divider resistance spools 98, 99, 100, 101,102, 103, 104, 105, 106 and 107 are provided in the transformer circuits as means for accurate adjustment of each voltage. A slide wire 108 having an arm 108a is located in the recorder 86 together with an amplifier 110 and CO pen positioning motor 112. The voltages from transformers 90 and 92 are connected in series to be additive and are impressed across points 108b and 1080 of the slide wire. The voltages from the transformers 88, 94 and 96 are connected in series and are impressed across the points 1086 and 108d of the slide wire with the voltages from transformers 88 and 96 being additive and that from transformer 94 being subtractive. The amplifier 110 senses small differences of voltage across its terminal and activates a recorder balancing motor to maintain a null balance point of the True CO recorder arm or pen 108a. Thus it is seen that this circuit utilizes the individual voltage signals proportional to the 0 CO and CO and multiplies these by the respective constants, sums the signals and compares the summations in such a way as to solve Equation 1. Other means may be used for this purpose such as by analog-computer systems and direct current calculating circuits.

In operation, the divider resistances of the circuit of FIGURE 2 are adjusted to give the desired voltages, the sampling probe 4 inserted in the kiln back housing wall 2, and the pump 22 started in operation. Wash water is drawn into the pump 22 from the Washer 18 and forces it through the orifice 28. The orifice 28 and recovery tube act as an aspirator to draw the hot dirty gas sample into the washer 18 where it is washed and thoroughly mixed with the water. The mixture of gas and water is discharged into the separator trap 36 where the water and a large portion of the dirt are separated from the gas sample and discharged to drain. From here part of the gas sample passes to the filter where it is heated above its dew point and small remaining dust particles removed prior to entering the analyzer cell block 52. The remaining part of the gas sample passes to the filter 56 where it is heated above its dew point and small dust particles removed. From here it passes through porous element gas filter 58 to the regulator which controls the rate of flow to the analyzer 62. The analyzers develop voltage signals proportional to the 0 CO and CO content of the gas and by use of the circuit of FIGURE 2 compute and record the True CO content of the gas on recorder 86.

While one embodiment of our invention has been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

1. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, an oxygen analyzer having means for producing a voltage signal proportional to oxygen content, a CO analyzer having means for producing a voltage signal proportional to CO content, a C0 analyzer having means for producing a voltage signal proportional to CO content, means connecting said conduit to each analyzer to feed a portion of said exit gas sample thereto, and means for modifying and comparing said voltages according to the equation (COg-f-CO) 100+ l.89CO4.78O

so as to obtain a signal proportional to True CO content of said exit gases.

2. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, an oxygen analyzer having means for producing a voltage signal proportional to oxygen content, a CO analyzer having means for producting a voltage signal proportional to CO content, a C0 analyzer having means for producing a voltage signal proportional to CO content, means connecting said conduit to each analyzer to feed a portion of said exit gas sample thereto, means for obtaining a fourth voltage proportional to 4.78 times said first voltage signal, means for obtaining a fifth voltage proportional to 1.89 times said second voltage signal, means for obtaining a sixth voltage proportional to 100 times said second voltage signal, means for obtaining a seventh voltage proportional to 100 times said third voltage signal, means for obtaining a constant voltage, means connecting said sixth and seventh voltages in series to be additive, means connecting said constant voltage and said fifth voltage in series to be additive and the said fourth voltage in series therewith to be subtractive, and means comprising the outputs of said last two means to obtain a signal proportional to True CO content of said exit gases.

3. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe located to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, a C0 analyzer connected in said second branch conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, and means for modifying and comparing said voltages to obtain the quotient of the equation so as to obtain a signal proportional to True CO content of said exit gases.

4. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe located to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, a C0 analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, means for obtaining a fourth voltage proportional to 4.78 times said first voltage signal, means for obtaining a fifth voltage proportional to 1.89 times said second voltage signal, means for obtaining a sixth voltage proportional to 100 times said second voltage signal, means for obtaining a seventh voltage proportional to 100 times said third voltage signal, means for obtaining a constant voltage, means connecting said sixth and seventh voltages in series to be additive, means connecting said constant voltage and said fifth voltage in series to be additive and the said fourth voltage in series therewith to be subtractive, and means comparing the outputs of said last two means to obtain a signal proportional to True CO content of said exit gases.

5. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, an infrared CO analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, said CO analyzer including a housing, means for delivering clean air at a predetermined constant rate and temperature to the inside of said housing, means providing additional voltages, and means for modifying and comparing said voltages according to the equation so as to obtain a signal proportional to True CO content of said exit gases.

6. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, an infrared CO analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, said CO analyzer including a housing, means for delivering clean air at a predetermined constant temperature to the inside of said housing, means for obtaining a fourth voltage proportional to 4.78 times said first voltage signal, means for obtaining a fifth voltage proportional to 1.89 times said second voltage signal, means for obtaining a sixth voltage proportional to 100 times said second voltage signal, means for obtaining a seventh voltage proportional to 100 times said third voltage signal, means for obtaining a constant voltage, means connecting said sixth and seventh voltages in series to be additive, means connecting said constant voltage and said fifth voltage in series to be additive and the said fourth voltage in series therewith to be subtractive, and means comparing the outputs of said last two means to obtain a signal proportional to True CO content of said exit gases.

7. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, means associated with said conduit for washing and removing dirt from said sample, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected to said first branch conduit, said analyzer including means for 6 producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, an infrared CO analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, a heated filter in said first branch conduit for filtering and heating said exit gases prior to being analyzed, a heated filter in said second branch conduit for filtering and heating said exit gases prior to being analyzed, means providing additional voltages, and means for modifying and comparing said voltages according to the equation co +co 100+1.89CO-4.78O2

so as to obtain a signal proportional to True CO content of said exit gases.

8. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, means associated with said conduit for washing and removing dirt from said sample, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, an infrared CO analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, a heated filter in said first branch conduit for filtering and heating said exit gases prior to being analyzed, a heated filter in said second branch conduit for filtering and heating said exit gases prior to being analyzed, means for obtaining a fourth voltage proportional to 4.78 times said first voltage signal, means for obtaining a fifth voltage proportional to 1.89 times said second voltage signal, means for obtaining a sixth voltage proportional to 100 times said second voltage signal, means for obtaining a seventh voltage proportional to 100 times said third voltage signal, means for obtaining a constant voltage, means connecting said sixth and seventh voltages in series to be additive, means connecting said constant voltage and said fifth voltage in series to be additive and the said fourth voltage in series therewith to be subtractive, and means comparing the outputs of said last two means to obtain a signal proportional to True CO content of said exit gases.

9. Apparatus for determining the True CO content of cement kiln exit gases comprising a probe supported to obtain a sample of said exit gases, a main conduit for said sample connected to said probe, means associated with said conduit for washing and removing dirt from said sample, a first branch conduit connected to said main conduit, a second branch conduit connected to said main conduit, an oxygen and CO analyzer connected in said first branch conduit, said analyzer including means for producing a voltage signal proportional to oxygen content of said gases and means for producing a voltage signal proportional to CO content of said gases, an infrared CO analyzer connected in said second conduit, said CO analyzer including means for producing a voltage signal proportional to CO content of said gases, a heated filter in said first branch conduit for filtering and heating said exit gases prior to being analyzed, a heated filter in said second branch conduit for filtering and heating said exit gases prior to being analyzed, said CO analyzer including a housing, means for delivering clean air at a predetermined constant temperature to the inside of said housing, means for obtaining a fourth voltage proportional to 4.78 times said first voltage signal, means for obtaining a fifth voltage proportional to 1.89 times said second voltage signal, means for obtaining a sixth voltage proportional to 100 times said second voltage signal, means for obtaining a seventh voltage proportional to 100 times said third voltage signal, means for obtaining a constant voltage, means connecting said sixth and seventh voltages in series to be additive, means connecting said constant voltage and said fifth voltage in series to be additive and the said fourth voltage in series therewith to be subtractive, and means comparing the outputs of said last two means to obtain a signal proportional to True CO content of said exit gases.

References Cited by the Examiner FOREIGN PATENTS 4/ 1963 Germany.

RICHARD C. QUEISSER, Primary Examiner.

ROBERT L. EVANS, Examiner. 

1. APPARATUS FOR DETERMINING THE TRUE CO2 CONTENT OF CEMENT KILN EXIT GASES COMPRISING A PROBE SUPPORTED TO OBTAIN A SAMPLE OF SAID EXIT GASES, A MAIN CONDIUT FOR SAID SAMPLE CONNECTED TO SAID PROBE, AN OXYGEN ANALYZER HAVING MEANS FOR PRODUCING A VOLTAGE SIGNAL PROPORTIONAL TO OXYGEN CONTENT, A CO ANALYZER HAVING MEANS FOR PRODUCING A VOLTAGE SIGNAL PROPORTIONAL TO CO CONTENT, A CO2 ANALYZER HAVING MEANS FOR PRODUCING A VOLTAGE SIGNAL PROPORTIONAL TO CO2 CONTENT, MEANS CONNECTING SAID 